Apparatus for separating the constituents of gaseous mixtures



May 15, 1934.

C. C. VAN NUYS APPARATUS FOR SEPARATING THE CONSTITUENTS OFGASEOUS MIXTURES Filed 13%. 14, 1933 INVENTOR CZaz/dc C Van (V g 6 ATTORNEYS Patented May 15, 1934 "PATENT OFFICE APPARATUS FOR SEPABATING THE CON- STITUENTS OF GASEOUS MIXTURES Claude C. Van Nuys, Crani'ord, N. .L, assignor to Air Reduction Company, Incorporated, New

York, N. Y., a corporation of New York Ap lication December 14,1933, Serial No. 702,307

Claims.

This invention relates to the separation and recovery of the constituents of gaseous mixtures, and particularly to the recovery of a constituent of intermediate boiling point in a condition of substantial purity by a continuous operation.

The invention may be utilized for the recovery of various constituents from complex gaseous mixtures, of which numerous examples are found in the art. It is especially useful in the recovery of products such as ethylene, which are produced admixed with various other hydrocarbon gases and hydrogen in the petroleum industry. By the application of the invention, ethylene can be recovered in a substantially pure condition and in an economical manner from various gaseous mixtures containing it.

It is the object of the invention, therefore, to provide a simple, efficient and economical apparatus for separating the constituents of complex gaseous mixtures, and particularly of recovering a constituent of intermediate boiling point in a substantially pure condition.

Another object of the invention is to provide an efiicient means for producing the refrigerative effect necessary for the accomplishment of the desired separation. 4

Further objects and advantages of the invention will be apparent as it is better understood by reference to the following specification.

The'invention depends upon the treatment of the gaseous mixture by liquefaction and rectification, so that constituents having diflerent boiling points are segregated. Thus the initial gaseous complex mixture, after compressing to a suitable pressure and primary cooling by heat exchange with products of the operation, is subjected to selective liquefaction with backward return of the liquefied constituents. By this step the initial mixture is separated into a liquid portion containing a substantial fraction of the constituents of intermediate boiling point and the major portion of the constituents whose boiling points are higher, and a gaseous fraction containing the balance of the constituents of the initial gaseous mixture.

The gaseous mixture resulting from the first step of the procedure is then subjected to further liquefaction with backward return of the liquid produced, thus effecting a further separation into liquid and gaseous fractions. These fractions are then further separated by rectification so as to produce an effluent consisting substantially of the constituents of lowest boiling point and a liquid containing substantially only constituents of intermediate and higher boiling points.

The liquid fraction from the rectification is then returned and subjected to rectification with the first fraction produced in the initial separation, the rectification being completed with liquid consisting substantially of the constituent of intermediate boiling point so as to produce an effluent consisting of that constituent in a substantially pure condition. The residual liquid produced by the final rectification consists almost entirely of the constituents of higher boiling point. The several fractions into which the gaseous mixture is thus separated are withdrawn continuously and are thus recovered and may be utilized for any desired purpose.

In the application of the procedure to the recovery of ethylene from gases derived from the petroleum industry, the major product is ethylene which has a boiling point intermediate between the boiling points of other constituents making It is to be understood that in the drawing no attempt has been made to illustrate those details of liquefaction apparatus which are well known to those skilledin the art, thedrawing being intended merely to elucidate the invention as hereinafter described.

Referring to-the drawing, 5 and 6 indicate columns in which the selective liquefaction and rectification of the gaseous mixture and the fractions thereof is accomplished. The initial gaseous mixture comprising the several constituents is compressed in a suitable compressor (not shown) to the pressure which may be necessary, and which will vary depending upon the nature of the gaseous mixture; The compressed gaseous mixture is introduced through a pipe 7 to an exchanger 8 wherein it is cooled by circulation about pipes 9, l0 and 11 through which the products Q of the separation at a lower temperature are dewardly through the pipes and accumulates in the chamber 13. It consists of a large portion of the constituent of intermediate boiling point, for example, ethylene, and the major portion of a con stituent or constituents having a higher boiling point.

The unliquefled residue is delivered to a head and passes through a pipe 16 into a cornpartment 17 at the bottom of the second column 6. Thence the gaseous mixture passes up-, wardly through pipes 18 surrounded by liquid produced in the subsequent rectification and is subjected to partial liquefaction. The liquid returns through the pipes into the compartment 17. The balance of the gaseous mixture is delivered to a head 19 and escapes through a pipe 20.

Liquid accumulating in the compartment 17 is delivered by a pipe 21, passes upwardly through an exchanger 22, thence through a pipe 23 and pressure reducing valve 24 and is delivered through a pipe 25 into the rectifying section of the column 6, in which it flows downwardly over trays 26 of the type usually. employed in rectification columns and in contact with rising vapors. The gaseous fraction escaping through the pipe 20 passes through an exchanger 27, pipe 28" and condenser 29, within the rectification column, being thus condensed to a liquid which es capes through a pipe 30 to an exchanger 31 where the liquid may be sub-cooled. The liquid passes then through a pipe 32, pressure reducing valve 33 and pipe 34 into the upper end of the rectification column and flows downwardly over the trays 26 therein in contact with rising vapors.

By the rectification in the upper section of the column 6 a separation is effected so that the eflluent' which escapes through pipe 35 at the top of the column consists substantially of the constituents having a boiling point lower than that of the constituent of intermediate boiling point, such as ethylene. The liquid which flows downwardly becomes concentrated in the constituents of, intermediate and higherboiling point, and this liquid flowing downwardly over the baiiles 36 finally accumulates in the compartment surrounding the tubes 18 at the bottom of the column. I

The eflluent escaping through the pipe 35 passes through the exchanger 31 where it serves to reduce the temperature of the liquid flowing in the opposite direction therethrough, thence through a pipe 37 to the exchanger 27, thence through a pipe 38 to the exchanger 22, and finally through a pipe 39 which delivers it to the pipe 9 in the exchanger 8. It is withdrawn after giving up its cold in the exchanger system through a pipe 40 as one of the products of the operation.

Liquid accumulating in the compartment 13 at the bottom of the column 5 is withdrawn through a pipe 41 and, after passing through a pressure reducing valve 42, is delivered to a separator 43. In the separator, vapors may escape from the liquid, and such vapors may be delivered through a pipe-44 to an intermediate point in the col- ,umn 5.

denser 48 through pipe 47 and valve 46 pass through pipe to the separator'43, whence they pass out through pipe- 44 to column 6 with the vapors previously mentioned.

The liquid from the separator 43 is delivered through a pipe 50 and valve 50a at an intermediate point in the rectification section of the colusual trays 51 in contact with vapors rising through the column. 1

Liquid from the lower part of the column dis delivered through a pipe 52 and valve 53 to the rectification section of the column 5, or, as. an alternative, vapors may be withdrawn also from a lower level or the column 6, above the liquid therein, through a pipe 54 and delivered through umn 5 wherein it. flows downwardly over thea valve 55 to the rectification section of the col- There are thus flowing into the rectification section of the column 5 fluids consisting principally of the constituents of intermediate and higher boiling points. Those fluids which are. liquid flow downward, tending to concentrate in' theconstituents of higher boiling point; those fluids which are gaseous flow upward and become concentrated in the constituent .01 intermediate boiling point, such as ethylene. The final rectification is accomplished with liquid flowing through the pipe 49, and the pressure reducing valve 49d, which consists substantially oi. the constituent of intermediate boiling point, so that the eiiluent escaping through the pipe 56 consists of the constituent of intermediate boiling point, for example ethylene, in substanial purity. This product may be'delivered through a pipe 57 to the pipe 11in the exchanger 8 and may be withdrawn through a pipe 58 and delivered to a suitable receptacle for storage, or it may be otherwise employed.

To facilitate the final rectification, a portion of the eflluent is diverted from the pipe 56 through a pipe 59, an after passing through an exchanger 60, it is delivered by a pipe 61 to comv pressor 62 where the. pressure is materially increased. The compressed eiliuent which may at this point be partially liquid is returned through a pipe 63 and the exchanger to a pipe 64 which delivers it to the condenser 48. The unliquefled portion of. this eflluent is partially liquefied in condenser 48 and is delivered through pipe 49 and pressure reducing valve 49d to the top of the rectifying section of the column 5. Thus the rectifying section is supplied continuously with a quantity of liquid consisting substantially of the constituent of intermediate boiling point, for example, ethylene. This liquid washes from the :rising vapors all constituents of higher boiling point, which are thus returned to the liquid flowing downwardly through thecolumn and accumulating therein about the pipes 14. The latter liquid is partially vaporized in cooling the initial gaseous mixture in the pipes 14, and the balance, if any, is withdrawn through apipe 65 and valve 65a which delivers it to the pipe 10 in the exchanger 8. The lower end product of the rectification column 5, over and above that portion withdrawn in the liquid state through pipe 65, is withdrawn in the vapor state through pipe 66 and regulative valve 67, after which it is added to the liquid portion coming through valve 65a. These combined products then enter pipe 10 of exchanger 8 wherein the vaporization of the liquid is completed, and the resulting product, consisting of the constituent or constituents of higher umn 6. Uncondensed vapors leaving a conboiling point, escapes through a pipe 68.

As examples of the practical application of the invention, I have utilized it to separate and recover ethylene from complex gaseous mixtures such as the following, in which the constituents are arranged in the order of their boiling points.

1 Gas Per cent H2 6-8 CH4 23-35 C2H4 23-26 CaHs 10-12 CaHe 15-18 CaHs 2-4 C4Ha 6-9 As well as small amounts of other constituents.

H2 33. 0 CH4 12. 5 C2H4 36. 5 Cal-Is 14. 0 CaHs 0. 5-1. 0 C4Ha 0. 3-0. '7

As well as small amounts of CzH: and other constituents.

III

draamcwmcn H2 -1 CH4 C2Hs CsHs 6. 1

CsHa C4Ha As well as small amounts of CzHa and other s ar constituents.

From such complex mixtures I have readily obtained ethylene of 98-99% purity with a yield of -85% and higher. The invention thus affords a convenient and economical apparatus for separating ethylene from mixtures of hydrogen and hydrocarbons which are available in larger quantities. The ethylene thus obtained may be utilized for a variety of commercial purposes.

From the foregoing description, it will be evident that the successive steps of separating the several constituents of the initial gaseous mixture are accomplished in a continuous manner, so as to effectively eliminate the constituents of lower boiling point and then to separate the constituents of higher boiling point, especially from the constituent of intermediate boiling point. The primary purpose of the invention is the recovery of the constituent of intermediate boiling point in a condition of substantial purity, and this is readily and economically accomplished by the procedure as described. v

Various changes may be made in the details of the apparatus, particularly in view of the special characteristics of the mixture treated, without departing from the invention orsacrificing any of the advantages thereof.

I claim:

1. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture initially to selective liquefaction with backward return to separate a liquid containing constituents of highest and intermediate boiling points, means for subjecting the'unliquefled residue of the gaseous mixture to a further selective liquefaction with backward return to separate a liquid and a gaseous fraction, means for separately liquefying the gaseous fraction, means for rectifying the liquids of the two fractions to separate the constituent of lowest boiling point thereby providing a liquid consisting principally of the constituent of intermediate boiling point, andmeans for rectifying the liquid consisting principally of the constituent of intermediate boiling point with the liquid produced by the first selective liquefaction to separate the constituent of intermediate boiling point as a gaseous eilluent.

2. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture initially to selective liquefaction with backward return to separate a liquid containing constituents of highest and intermediate boiling points, means for subjecting the unliquefied residue'of the gaseous mixture to a further selective liquefaction with backward return to separate a liquid and a gaseous fraction, means for sepa rately partially liquefying the gaseous fraction,

means for rectifying the liquids of the two fractions to separate the constituent of lowest boiling point thereby providing a liquid consisting principally of the constituent of intermediate boiling point, means for rectifying the liquid consisting principally of the constituent of intermediate boiling point with the liquid produced by the first selective liquefaction to separate the constituent of intermediate boiling point as a gaseous emuent, and means for reliquefying a portion of the effluent to provide reflux liquid for the last mentioned rectification.

3. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous'mixture initially to selective liquefaction with backward return to separate a liquid containing constituents of highest and intermediate boiling points,-means for separating vapors from the liquid, means for subjecting the unliquefied residue of the gaseous mixture to a further selective liquefaction with backward return to separate a liquid and a gaseous fraction, means for rectifying the liquids of the two fractions to separate the constituent of lowest boiling point thereby providing a liquid consisting principally-of the constituent of intermediate boiling point, and means for rectifying the liquid consisting principally of they constituent of intermediate boiling point with the liquid produced by the first selective liquefaction to separate the constituent of intermediate boiling point as'a gaseous efliuent.

4. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture initially to selective liquefaction with backward return to separate aliquid containing constituents of highest and intermediate boiling points, means for subjecting the unliquefied residue of the gaseous mixture to a further selective liquefaction'with backward return to separate a liquid and a gaseous fraction, means for separately liquefying the gaseous fraction, means for rectifying the liquids of the two fractions to separate the constituent of lowest boiling point thereby providing a liquid consisting principally of the constituent of intermediate boiling point, means for utilizing the low temperature of the separated constituent of lowest boiling point to cool the liquefled fractions before rectification, and means for rectifying the liquid consisting principally of the constituent-of intermediate boiling point with the liquid produced by the first selective liquefaction to separate the constituent of intermediate boiling point as a gaseous efiluent.

5. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture initially to selective liquefaction with backward retum' to separate a liquid containing constituents of highest and intermediate boiling points, means for subjecting the unliquefied residue of the gaseous mixture to a further selective liquefaction with backward return to separate a liquid and a gaseous fraction, means for separately liquefying the gaseous fraction, means for rectifying the liquids of the two fractions to separate the constituent of lowest boiling point thereby providing a liquid consisting principally of the constituent of intermediate boiling point, and means for rectifying the liquid consisting principally of'the constituent of intermediate boiling point with the liquid produced by the first selec tive liquefaction to separate the constituent of intermediate boiling point as a gaseous efiluent and means for delivering vapors from the liquid consisting principally 'of the constituent of intermediate boiling point to the last mentioned rectifying means.

6. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture to selective liquefaction with backward retum in two successive and independent steps thereby producing two liquids of different compositions, means for liquefying the residue of the gaseous mixture after the second selective liquefaction, means for rectifying the liquid produced by the second selective liquefaction with the liquefied residue, thereby producing a liquid rich in the constituent of intermediate boiling point, and means for rectifying the latter liquid with the liquid produced by the first selective liquefaction of the gaseous mixture to separate the constituent of intermediate boiling point as a gaseous eflluent.

'7. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture to selective liquefaction with backward return in two successive and independent steps thereby producing two liquids of different composition, means for liquefying the residue of the gaseous mixture after the second selective liquefaction, means for rectifying the liquid produced byfthe second selective liquefaction with the lique-' fied'residue thereby producing a liquid rich in e the constituent of intermediate boiling point,

means for rectifying the latter liquid with the liquid produced by the first selective liquefaction of the gaseous mixture to separate the constituent of intermediate boiling point as a gaseous eflluent, and means for reliquefying a portion of the efiluent to provide reflux liquid for the last mentioned rectification.

8. An apparatus for separating the constituents residue thereby producing a liquid rich in the constituent of intermediate boiling point, means for rectifying the latter liquid with the liquid produced by the first selective liquefaction of the gaseous mixture to separate the constituent of intermediate boiling point as a gaseous efliuent, and means for reliquefying a portion of the effluent to provide reflux liquid for the last mentioned rectification. I

9. An apparatus for separating the constituents of gaseous mixtures including at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture to selective liquefaction with backward return in two successive and independent steps thereby producing two liquids of difierent compositions, means for liquefying the residue of the gaseous mixture after the second selective liquefaction, means for rectifying the liquid produced by the second selective liquefaction with the liquefied residue, thereby producing a liquid rich in the constituent of intermediate boiling point, and

means for withdrawing the latter liquid with the liquid produced by the first selective liquefaction of the gaseous mixture to separate the constituent of intermediate boiling point as a gaseous efiluent.

10.,An apparatus for separating the constituents of gaseous mixtures including 'at least three constituents having different boiling points, which comprises means for subjecting the gaseous mixture to selective liquefaction with backwardreturn in two successive and independent steps thereby producing two liquids of different composition, means for separating vapors from the liquid produced by the first selective liquefaction, means for delivering the vapors to rectifying means first hereinafter mentioned, means for liquefying the residue of the gaseous mixture after the second selective liquefaction, means for rectifying the liquid produced by the second selective liquefaction with the liquefied residue thereby producing a liquid rich in the constituent of intermediate boiling point, means for rectifying the latter liquid with the liquid produced by the first selective liquefaction of the gaseous mixture to separate the constituent of intermediate boiling point as a gaseous eilluent,. and means for reflux liquid for the last mentioned rectification.

CLAUDE c. VAN NUYS. 

